1. Field of the Invention
This invention relates to patterned platelets. More particularly the invention relates to platelets having specified shapes, sizes and optical properties, optionally with markings thereon, such that the platelets can be applied to objects to tag and identify the objects with unique codes. The platelets can be pigments in inks or paints applied to an object. The platelets can also be mixed in with other materials to tag them such as in liquids or solids.
2. Description of the Related Art
Counterfeiting of articles and documents has been a problem in the past. Further, it is also useful in many industries to be able to trace of the origin of goods and documents. In the past, many methods have been introduced to tag articles such that they can be easily and positively identified in the future and to prevent tampering or counterfeiting activities. Some of these methods including using flop colors and holograms on platelet pigments. For example, the recently issued U.S. currency has flop colors.
Presently most platelet pigments are made in sheets or films and then broken into random sized fragments buy various techniques such as sand grinding, ball milling, two roll milling, pestle and mortar or freezing and cracking. These fragments are then sieved by screens or wet sieving or air classification to sort the sizes of the fragments. However the shapes of the fragments are random and the size of the fragments has a wide standard deviation. Further, the various sieving steps add to the cost of processing the platelets.
Marking of platelets of even size and shape was not used to identify those platelets and use the platelets in codes to help identify articles and substances and deter counterfeiters.
One recent development was to make controlled shape and size platelet pigments by molding polymers as shown in patent WO98/12265 however the molding process is difficult to use, wastes a lot of expensive material and is costly. Another drawback is removing odd shaped, notched or angled pieces from the mold.
Patterned platelets, having controlled shapes and sizes, have not been coded by spatial features, such as raised or lowered portions of the patterned platelets with identifiable shapes on the platelets or spectral features, such as color and polarization, to deter counterfeiters.
Low cost, easy to make, coded platelets, which can be easily applied to articles or documents such that they are easily detected are needed.
Three dimensional shaped patterned platelets have not been used in the past. Three-dimensional platelets add more possibilities for coding with more shapes and the shapes may be useful for reflecting or refracting light.
Low cost, easy to make, coded platelets, which can be mixed into liquids and solids to identify them are needed. The platelets can be used in inks and paints applied to objects to identify the objects.
Most prior art Cholesteric Liquid Crystal (CLC) pigments are made by actinic methods on sheets of material. The sheets are then broken up into fragments of random sizes and then sieved to obtain particles of approximately the same size and to eliminate platelets which are too small. This process results in a lot of wasted materials which are costly to make.
It will be appreciated that prior art platelet pigments cannot cost effectively produce the ultra-narrow size distribution, have not taught low cost easy to make the production of platelets with regular shapes, and they have not taught how pigments can be endowed with markings or codes using spatial marks, polarization or spectral marks.
This invention relates to producing platelets, which have a uniform shape and size. Platelets produced with a uniform size do not have to be sieved, the resulting standard deviation in the size of the platelets is smaller than the platelets produced with random sizes and then sieved. When platelets are produced with a small standard deviation of size, codes comprising mixes of several sizes of platelets in various percentages can be made for tagging objects.
Similarly when distinct shapes of platelets are made, they can be applied to objects, to tag those objects. For example, a mix of 50% circles and 50% squares can be one code. The letters B, K, Y could be another code. A mix of numbers, letters and shapes could be yet another code. Any combinations unique to a product can then identify that product when platelets using that code are applied to or embedded in the product.
In addition to the size and shape of the platelets, platelets can also be made with spatial markings, either raised or lowered portions, on the platelets such as having letters or shapes etched on the platelets. The platelets can also have apertures in the platelets or notches on the perimeter of the platelets to further distinguish them and make them more useful for tagging.
The platelets can also be made to reflect distinctive portions of the spectrum of light to further identify the platelets for tagging purposes. Each platelet can have one or more sections of its surface reflect different spectral codes. CLC platelets can be made to selectively reflect wide or narrow bands of light. For example, platelets can be made to reflect red or green or blue or white light or even light not in the visible spectrum. A platelet can have one section reflect green right circularly polarized light and another section reflect blue left polarized light. The light reflected can be used to easily identify the platelets used. Patterns of colors of light reflecting pigments can be used to further code the platelets. By using dopant materials in the CLC platelets, spectral band absorbing identifiers can be placed in the platelets further coding the platelets to be used as tags.
The sizes, shapes and spatial markings on the platelets can be made by masking when an actinic process of CLC production is used.
Other techniques for producing specified shapes and sizes of platelets include the use of masking by screen printing, masking by ink jet printing, gravure printing, chemical etching, ablating, and laser cutting methods all of which are well know in the art. Any additive or subtractive methods used for making the patterned platelets, either alone or in some combination, are within the scope of the invention. To make three dimensional shaped patterned platelets stereolithography methods of adding and subtracting layers of material may be used.
It is therefore an object of this invention to provide platelets having predetermined regular shapes.
Another object of this invention is to produce platelets having substantially identical lateral dimensions or areas, resulting in a very narrow platelet size distribution.
Another object of this invention is to provide platelets with substantially identical sizes and shapes in two or three dimensions.
Another object of this invention is to reduce the cost of producing pigments by eliminating milling and sieving steps.
Another object of this invention is to eliminate production of platelets outside a desired range, thus reducing waste.
Another object of the invention is to produce patterned platelets without using expensive hard to use molds.
Yet another object of this invention is to provide platelets of known size and shape in combinations of different sizes and or shapes to form codes used for tagging objects.
Yet another object of this invention is to provide platelets of known size and shape having spatial markings on the platelets for additional identification codes.
Yet another object of the present invention is to provide platelets of known size and shape having identification codes created by means of polarization or spectral encoding.
Yet another object of this invention is to provide platelets for general printing and in particular, security printing wherein the platelet shape, size spatial, spectral and polarization encoding identifies the origin of the ink.
It is a further object of the invention to provide codes wherein inks or paints with coded platelets are placed in specified locations on a product thus forming another code.
It is yet another object of the invention to provide optical properties in the three dimensional shaped:patterned platelets.